Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$55.75	11.314%	$62.0576	$62.06	$62.05	$62.10
Purchase #2	$84.80	11.854%	$94.8522	$94.85	$94.85	$94.90
Purchase #3	$55.58	7.777%	$59.9025	$59.90	$59.90	$59.90
Purchase #4	$185.77	10.632%	$205.5211	$205.52	$205.50	$205.50
Purchase #5	$186.42	12.153%	$209.0756	$209.08	$209.10	$209.10
Purchase #6	$146.47	5.426%	$154.4175	$154.42	$154.40	$154.40
Purchase #7	$175.60	5.474%	$185.2123	$185.21	$185.20	$185.20
7 purchase totals =	$890.39		$971.0388	$971.04	$971.00	$971.10